Virtually all air intake systems require an air filtering mechanism to maintain inlet air free of contaminants. This requirement is particularly true of shipboard engines and ventilation systems that operate in a salt spray environment, where moisture and salt particles impinging, for example, on fast spinning turbine blades can cause severe damage to the ship's propulsion system. In this environment, the filtering mechanism must be able to separate moisture from the inlet air, providing dry and clean air to the ship's propulsion system or ventilation system. This requirement is equally important in trains, offshore platforms, and other wet environments, among other applications.
In a specific example of a shipboard application, most naval vessels rely on fossil fuel for propulsion, and many of these vessels are powered by gas turbines. Gas turbine engines require significant quantities of air for combustion. This air is drawn into the combustion chamber through an air intake. The air intake, ideally, would be as high as possible above the waterline to minimize the possibility of water entrainment (i.e., entrainment of ocean spray) in the intake air stream. Because the air intakes are located high on the ship, their weight should be minimized to avoid making the ship less stable and more susceptible to rolling, and in a worst case scenario, capsizing.